The aim of this study was to construct an expression vector carrying the
hypoxia/radiation dual‑sensitive chimeric
hypoxia response element (HRE)/early growth response 1 (Egr‑1) promoter in order to overexpress the therapeutic second mitochondria‑derived activator of
caspases (Smac). Using this expression vector, the present study aimed to explore the molecular mechanism underlying radiotherapy‑induced A549 human
lung adenocarcinoma cell death and apoptosis under
hypoxia. The plasmids, pcDNA3.1‑Egr1‑Smac (pE‑Smac) and pcDNA3.1‑HRE/Egr-1‑Smac (pH/E‑Smac), were constructed and transfected into A549 human
lung adenocarcinoma cells using the
liposome method. CoCl2 was used to chemically simulate
hypoxia, followed by the administration of 2 Gy X‑ray irradiation. An MTT assay was performed to detect cell proliferation and an
Annexin V‑fluorescein
isothiocyanate apoptosis detection kit was used to detect apoptosis. Quantitative polymerase chain reaction and western blot analyses were used for the detection of
mRNA and
protein expression, respectively.
Infection with the pE‑Smac and pH/E‑Smac plasmids in combination with radiation and/or
hypoxia was observed to enhance the expression of Smac. Furthermore, Smac overexpression was found to enhance the radiation‑induced inhibition of cell proliferation and promotion of cycle arrest and apoptosis. The cytochrome c/caspase‑9/caspase‑3 pathway was identified to be involved in this regulation of apoptosis. Plasmid
infection in combination with X‑ray irradiation was found to markedly induce cell death under
hypoxia. In conclusion, the
hypoxia/radiation dual‑sensitive chimeric HRE/Egr‑1 promoter was observed to enhance the expression of the therapeutic Smac, as well as enhance the radiation‑induced inhibition of cell proliferation and promotion of cycle arrest and apoptosis under
hypoxia. This apoptosis was found to involve the mitochondrial pathway.